1. Field of the Invention
The present disclosure relates to the field of electrical power transmission, and particularly to an induction coil assembly and a wireless power transfer system.
2. Description of the Related Art
A magnetic resonance wireless power transfer system is shown in FIG. 1. In order to effectively transfer energy from a power transmitting terminal to a power receiving terminal, the power transmitting terminal is provided with a compensation capacitor Cs, and the compensation capacitor Cs and a transmitting coil inductor Ls resonate at a system operation frequency f0 (such as a frequency of 6.78 MHZ which is prescribed in standards of Wireless Power Consortium and Alliance for Wireless Power). Similarly, the power receiving terminal is also provided with a compensation capacitor Cd, and the compensation capacitor Cd and a receiving coil inductor Ld also resonate at the frequency f0. According to the circuit in FIG. 1, a coil of the power transmitting terminal and a coil of the power receiving terminal are coupled in a magnetic resonance manner at a same frequency, so that the electrical power from the transmitting side is transferred to a load at the receiving side for using.
According to the abovementioned magnetic coupling process, an alternating magnetic field is generated by the coupling of the receiving coil of the receiving side and the transmitting coil, an induced voltage Ud of the alternating magnetic field is expressed by the following equation:Ud=ω0*Ip*k*√{square root over (Ls*Ld)}
Wherein, ω0 denotes a resonance frequency, Ip denotes a current in the transmitting coil, k denotes a coupling coefficient between the transmitting coil and the receiving coil, Ls denotes an inductance value of the transmitting coil, and Ld denotes an inductance value of the receiving coil.
As can be seen from the abovementioned equation, in a case where the operation frequency is fixed and the transmitting current in the transmitting coil is constant, in order to increase the voltage induced by the receiving coil, it is necessary to optimize the structure of coil, in particular the structure of the receiving coil, so as to improve the magnetic field coupling ability of the receiving coil. Therefore, designers have to, within an effective range, on the one hand improve the inductance value Ld of the receiving coil, and on the other hand improve the coupling coefficient k between the transmitting coil and the receiving coil.